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Search: id:A081460
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| A081460 |
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Consider the mapping f(r) = (1/2)*(r + N/r) from rationals to rationals where N = 5. Starting with a = 2 and applying the mapping to each new (reduced) rational number gives 2, 9/4, 161/72, 51841/23184, ..., tending to N^(1/2). Sequence gives values of the denominators. |
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+0
3
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| 1, 4, 72, 23184, 2403763488, 25840354427429161536, 2986152136938872067784669198846010266752, 39878504028822311675150039382403961856254569551519724209276629577579916539
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Related sequence pairs (numerator, denominator) can be obtained by choosing N = 2, 3, 6 etc.
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FORMULA
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a(n)=2*a(n-1)*A081459(n-1) - Mario Catalani (mario.catalani(AT)unito.it), May 21 2003
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PROGRAM
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(PARI) {r=2; N=5; for(n=1, 8, a=numerator(r); b=denominator(r); print1(b, ", "); r=(1/2)*(r + N/r))}
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CROSSREFS
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Cf. A000129, A001333, A081459.
Sequence in context: A024257 A152653 A087315 this_sequence A055556 A089665 A092871
Adjacent sequences: A081457 A081458 A081459 this_sequence A081461 A081462 A081463
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 22 2003
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EXTENSIONS
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Edited and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 06 2003
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